Adults with intellectual disabilities in the UK are more likely to be obese than their non-disabled peers and are at risk of experiencing serious medical conditions such as heart disease, stroke and Type 2 diabetes. UK weight management guidance recommends multi-component weight management interventions, tailored for different population groups. The aim of this thesis was to explore how evidence-based multi-component weight management interventions can be tailored for adults with intellectual disabilities who are obese. The thesis comprised three phases. Phase One included an integrative review of evidence-based multi-component weight management interventions for adults with intellectual disabilities; an exploration of theories used to underpin weight management interventions for this population; and a mapping exercise to investigate the extent of weight management service provision for adults with, and without, intellectual disabilities. The review found emerging evidence to suggest that multi-component weight management interventions can be tailored and are effective for adults with intellectual disabilities. However, the review identified few studies (n=5) and none of the identified studies explored this population’s views and experiences of such interventions. Phase One also found gaps in underpinning theories and insufficient service provision for this population. Phase Two comprised three studies to explore participants’ views and experiences of the barriers and facilitators to weight management for adults with intellectual disabilities. These studies included a qualitative study involving interviews with 14 health care practitioners; a co-produced focus group qualitative study involving 19 adults with intellectual disabilities and 8 of their carers; and a survey involving 19 carers and support workers. Thematic analysis of participants’ responses highlighted their frustrations with several barriers including a lack of accessible healthy lifestyle information, a lack of resources, a lack of reasonable adjustments, inconsistencies in caring support, unmet training needs for carers and support workers, and socio-economic and environmental barriers. Facilitators included the provision of clear and accessible healthy lifestyle information, provision of resources, consistent caring support, reasonable adjustments, and training for carers, support workers and health care practitioners. Phase Three involved a synthesis of findings from Phases One and Two. The overall findings imply that it is inequitable support and barriers associated with complex systems-related issues, rather than poor lifestyle choices or a lack of motivation, which inhibits this population from managing their weight if they want to. A whole systems approach is needed to address the systems-related issues and barriers experienced by this population, rather than a sole reliance on non-evidence-based weight management interventions (such as diet-only or exercise-only interventions) focused primarily on individual behaviour change to achieve short-term weight loss. The thesis has implications for research, policy and practice. It presents a whole systems approach and a logic model outlining the types of systems-related activities needed at several levels to overcome identified barriers and to contribute to reductions in the inequities and inequalities experienced by adults with intellectual disabilities who want to manage their weight.

Background: Acceptance is understood to be an important element in coping with chronic illnesses, linked to positive outcomes such as reduced symptoms and greater quality of life. Chronic Fatigue Syndrome (CFS) is a disabling syndrome that is associated with a poor reported quality of life even in comparison to other chronic conditions. Given that Acceptance and Commitment Therapy (ACT) is a psychotherapeutic model aimed at increasing psychological flexibility, with an emphasis on experiential acceptance and the pursuit of values, this approach holds potential for living and coping with CFS. Methods: This study used a mixed method multiple single case design to explore the effects of a six week self-help ACT intervention with six participants with CFS. Results: Significant increases in ‘engaged response style’ was replicated in four out of six participants and maintained at follow up, with the qualitative data adding further validity to the importance of the values component of the intervention. Low initial acceptance scores improved in four participants but were not maintained. Overall measures of psychological flexibility indicated improvements maintained at follow up for three participants. All participants wearing the activity monitor showed increased physical activity post-intervention, three of which maintained this at follow up. Five participants reported less symptoms and disability, which was maintained for three participants. The implicit measure indicated that underlying beliefs remained stable. Conclusion: This study was largely exploratory but it seems that this intervention might be of benefit to some individuals with CFS, particularly in the promotion and pursuit of individual values. This study adds support to the role of acceptance in CFS however in this format at least it seems that any benefits from the intervention are difficult to maintain. Although improvements in overall psychological flexibility were replicated in three out of six participants, this prompts discussion about the ineffectiveness of the intervention for other participants.

Mental toughness (MT) originated within elite sport and was identified as an attribute of success. MT has emerged as being important for enhancing health-related lifestyle factors (HRLF; e.g., physical activity). Investigating the healthiness of one’s lifestyle appears a timely area to research given the current health status of the population. Therefore, the aim of this thesis was to investigate MT in relation to HRLF and weight loss. Study One investigated MT and HRLF in university students (n = 167). Self-reported MT, physical activity, exercise barriers, dietary behaviour, and psychological wellbeing were recorded. MT was significantly different between regular exercisers (M = 3.43 ± .42) and non-regular exercisers (M = 3.24 ± .54, p < .05). Components of eating identity, exercise barriers, and psychological wellbeing, were significantly correlated with MT. Study Two longitudinally investigated weight loss progress, and adherence to a weight loss support group, in slimming club members who were pursuing a weight loss goal (n = 132). MT and eating identity were assessed at baseline, three-months, and six-months, and weight was recorded at weekly meetings. Overall MT was not significantly related to weight loss (r = -.15, p > 0.05) or adherence to the service (r = .03, p > 0.05). Study Three sampled individuals who held a weight loss goal, but were not attending a weight loss support club (n = 78). Overall MT was not significantly related to weight loss (r = -.21, p > 0.05). MT was not significantly different between weight loss goal achievers (M = 3.62 ± .49) and non-goal achievers (M =3.42 ± .38, p > 0.05). Thus, irrespective of whether structured support is received, overall MT was not related to weight loss progress. II Study Four investigated the experiences of high (n = 9) and low (n = 7) mentally tough individuals pursing a weight loss goal. High and low MT individuals, identified using the MTQ48, were interviewed. Thematic analysis revealed that amongst the high mentally tough individuals, those who prioritised leading a healthy lifestyle reported weight loss success compared to those who prioritised other goals. Strategies to overcome low levels of MT (e.g., control), as well as receive additional support, appeared crucial for successful weight loss in low MT individuals. Study Five further investigated the low MT individuals’ (n = 7) perceptions, experiences, and attitudes, towards weight loss. Low MT individuals were sampled based on their MT score assessed via the MTQ48. Vignette based interviews extended the findings in Study Four. Thematic analysis revealed key findings, including the potential to change low MT individuals’ perceptions to enhance behaviour change. Overall, this thesis expanded the understanding of MT; the processes that one experiences when trying to lose weight appears to differentiate between high and low MT individuals, which offers an explanation as to why MT did not appear to play a significant role in weight loss outcomes. These findings challenged the predominant contemporary understanding of MT and demonstrated that MT was not associated with behaviour change to achieve weight loss.